Contribution of Arbuscular Mycorrhizal Fungi to Sustainable Maize Production in the Low-Fertility Ultisols of Thailand

Restrictions on crop production in Ultisols are primarily driven by low soil fertility, which leads to the unsustainable use of soil resources and food insecurity. Significantly, arbuscular mycorrhizal fungi (AMF) enhance nutrient availability for plants, which in turn contributes to greater soil productivity and supports sustainable crop production. This study aims to evaluate the effects of AMF inoculation combined with chemical fertilisation on maize growth and yield in three series of Ultisols. A pot experiment was performed with a 2 × 3 factorial CRD with five replications. Two factors were studied as follows: (1) AMF (Glomus sp.) (non-AMF and AMF inoculation) and (2) rates of chemical fertiliser (0, 50, and 100% of the recommended fertiliser rate for maize, CF). The results showed that AMF significantly enhanced the growth and yield of maize at all CF rates for all soil series at p ≤ 0.01. Total biomass and grain yield following AMF treatment were markedly higher than yields obtained without treatment. Likewise, AMF significantly improved the photosynthetic physiology and NPK content of maize. The CF rate had a negative impact on AMF root colonisation, and AMF efficiency also decreased as the CF rate increased. The relative mycorrhizal dependency (RMD) on maize growth and yield was the highest at 0% CF, with averages of 34.49% and 52.35%; however, these values decreased to 7.43% and 8.73% at 100% CF, respectively. Despite this, the RMD of maize growth and yield remained positive for all soil series. These findings suggest that AMF are an effective means of supporting sustainable maize cultivation in Ultisols.